Method for testing a network, and corresponding network

ABSTRACT

A method for testing a network made up of network nodes and devices connected to network nodes, has the steps:  
     determining the network topology, using at least the network topology, using at least the number of network nodes, the network-node identity, and the wiring of the network-node inputs and outputs;  
     comparing a current network topology to a permanently stored, reference network topology for the network, in order to detect a change in the number and/or type of devices connected to the network, in the number and/or type of network topology, and/or in the number and/or type of network nodes at which a change is present.

[0001] The present invention relates to a method for testing a network,which is made up of network nodes and devices connected to networknodes, the network topology being determined by at least the number ofnetwork nodes, the network-node identity, and the interconnectionconfiguration of the network-node inputs and outputs.

[0002] The present invention also relates to a network having networknodes interconnected in a network topology and devices at the networknodes; each network node having memory to store data for indicating atleast the network-node identity, and the network being designed fordetermining the current network topology, using at least the number ofnetwork nodes, the network-node identity, and the interconnectionconfiguration of the network-node inputs and outputs, by reading out thememory of the network nodes and evaluating the progress of the datatransmission during the reading-out.

[0003] The IEEE-1394 standard describes a network, which has networknodes and offers a serial bus connection between different devices thathas a high data-transmission rate. Such a network is also known by thename of FireWire or iLink. The network is essentially made up of networknodes, which have one or more network-node outputs. The network nodesmay be contained in devices, such as a radio, monitor, CD player, etc.Additional network nodes may be connected to network-node inputs andoutputs.

[0004] The superordinate node of a network is referred to as a root. Inprinciple, any node may become the root. In the topology, two nodes havea child and parent relationship to each other, i.e. the superordinatenode is designated as a parent, and the subordinate node is designatedas a child. Therefore, a node may simultaneously be the parent of onenode and the child of another node.

[0005] Network nodes that are only connected to one additional networknode are referred to as terminal nodes. Network nodes having two or morenetwork nodes connected are designated as brunch.

[0006] The network forming the basis of the present invention isdesigned to independently configure itself without a host processor, thedetermination of the network topology, i.e. the configuration of thenetwork, being carried out after the network is reset. A reset of thenetwork is initiated when, for example, a device or network node isremoved from the network or an additional device or network node isadded to the network. The configuration of a network is usually carriedout in three steps:

[0007] 1. Bus Initialization:

[0008] The bus initialization is triggered by a reset command, theindividual network nodes transmitting the reset signal to the othernetwork nodes. All information regarding the previous network topologyis deleted in the network nodes, and the network nodes are shifted intothe initialization state.

[0009] 2. Branch Identification:

[0010] During the branch identification, the topology of the network isdetected, and the relationship of the network nodes to each other isidentified. The independent identification of the network nodes asparent and child with respect to each other allows a root network nodeto be defined as a starting node, which assumes the bus management ornetwork management.

[0011] 3. Self-Identification:

[0012] To manage the network, the network topology and the physicalcharacteristics of the network nodes must be known. To this end, thenetwork nodes transmit the most important physical characteristics in aself-ID packet during self-identification. The transmission of the dataregarding the individual network nodes occurs in the order of thetopology configuration of the network, so that the position of thenetwork nodes in the network may be identified. The root network nodestores the number of network nodes connected and their self-ID packetinside the topology map. The network topology, network-node numberphy_id, and the physical characteristics of the network nodes connectedmay be extracted with the aid of the topology map.

[0013] A register memory, in which a network-node identification numberor device identification number and further information regarding thenetwork or the device are stored, is provided in each network node forthe network configuration. Each device or each network node is providedwith an unequivocal identification of the manufacturer, vendor ID, whichis likewise stored in the register memory. In addition, a unique number(chip ID) of the integrated circuit, in which the hardware and softwarefor producing the network node is incorporated, is stored in theregister memory. The physical characteristics of the network node andthe states of the corresponding network outputs (ports) may be input inthe register memory as additional information items. The characteristicsmay include, for example, speed (sp=speed), delay time (del=delay),pause interval (gap-cnt=gap-count), voltage class (pwr=power class),etc.

[0014] As a rule, the root network node is provided with a registermemory for storing the so-called network-topology map, which the numberof network nodes connected and the information transmitted from thenetwork nodes to the root network nodes regarding the characteristics ofthe specific network nodes (self-ID packets). In this connection, eachnetwork node is assigned a network-node number phy_id by the rootnetwork node. The information items (self-ID packet) transmitted by anetwork node to the root network node include network-node number(phy_id), pause number (gap-cnt), speed (sp), delay (del), voltage class(pwr), as well as additional information.

[0015] In this manner, data may be transmitted by a network node toanother network node.

[0016] A serial bus is defined by the IEEE-1394 standard. Examples ofsimilar buses include MOST, HiQoS, CAN, Universal Serial Bus (USB),etc., which likewise represent a network of the species.

[0017] In conventional networks, a reset of the network is carried outafter the network topology is changed, e.g. by adding or removingdevices, and the information regarding the previous network topology islost. This is especially problematic when external devices are added orthe network is manipulated.

[0018] Therefore, the object of the present invention is to specify amethod for testing a network of the species, where changes to thenetwork and to the connected devices and network nodes may beidentified.

[0019] The object is achieved by the method of the present invention, inthat a current network topology is compared to a reference networktopology stored for the network, in order to detect a change in thenumber and/or type of devices connected to the network, a change in thenumber and/or type of network topology, and/or a change in the numberand/or type of network nodes at which a change is present.

[0020] Therefore, it is proposed that a reference network topology bepermanently stored, which is not modified or erased in response to thenetwork being reset. In this manner, the current network topology may becompared to the reference network topology, and changes to the networkmay be detected.

[0021] A reference network topology is advantageously stored on demandby accepting a current network topology as the reference networktopology, in that the data for the current network topology are read infrom a central network-topology memory for the network, and fromdecentralized network-node memories, and the data read in are stored ina reference network-topology memory.

[0022] The testing of the network is automatically carried out inresponse to a reinitialization of the network.

[0023] The comparison of the current network topology to the referencenetwork topology is preferably carried out by comparing the content ofthe data stored in a network-topology comparison memory and a referencenetwork-topology memory. In doing this, the data for the current networktopology are read in from a central network-topology memory for thenetwork and from decentralized network-node memories, and stored in anetwork-topology comparison memory.

[0024] It is particularly advantageous for the reference networktopology to be restored by automatically deactivating network nodes,network-node outputs, and/or devices at the network-node outputs, whichare not provided in the reference network topology. This not only allowsthe network to be tested, but also protects the network frommanipulation and precludes it from being misused by improper, externaldevices.

[0025] The method is preferably applied to a network corresponding tothe IEEE-1394 standard, but may equally be used for Universal Serial Bus(USB networks) or MOST networks, etc.

[0026] According to the present invention described above, a memory forpermanently storing a reference network topology for the network and acomparator for comparing the current network topology to the referencenetwork topology are provided in the network of the species, in order totest the network and detect a change in the number and/or type ofdevices connected to the network, in the number and/or type of networktopology, and/or in the number and/or type of network nodes at which achange is present.

[0027] The network is preferably designed to automatically store thedetected, current network topology on demand as a reference networktopology, in the memory for the reference network topology. In thismanner, a current network topology recognized as being permissible isdefined as the reference network topology for future tests.

[0028] In addition, the network is preferably designed for automatictesting of the network after a reinitialization or after the addition orremoval of a network component.

[0029] Furthermore, it is advantageous for a network-topology comparisonmemory for storing the detected, current network topology to be providedin the network, in particular in a root network node. The comparator isthen designed to compare the contents of the data, which are stored inthe network-topology comparison memory and the referencenetwork-topology memory.

[0030] It is especially advantageous that the network and, inparticular, the network nodes are designed to restore the referencenetwork topology by automatically deactivating network nodes,network-node outputs, and/or devices at the network-node outputs, whichare not provided in the reference network topology.

[0031] The network preferably corresponds to the IEEE-1394 standard orother appropriate standards, such as the Universal Serial Bus Standard(USB, MOST, HiQoS, CAN, etc.).

[0032] Using a network corresponding to the IEEE-1394 standard as anexample, the present invention is explained below in detail on the basisof the enclosed drawings. The figures show:

[0033]FIG. 1 a schematic representation of a simple network having sixnetwork nodes;

[0034]FIG. 2 a schematic representation of the modified network fromFIG. 1;

[0035]FIG. 3 a sketch of the method for reading a current networktopology into the network-topology comparison memory;

[0036]FIG. 4 a sketch of the method for initializing the referencenetwork topology and checking the current network topology;

[0037]FIG. 5 a tabular representation of the memory contents of thenetwork topology map according to the 1394 standard;

[0038]FIG. 6 a tabular representation of the data packet, self-IDpacket, transmitted by the network nodes according to the 1394 standard;

[0039]FIG. 7 the minimum content of the register memory for the networkcharacteristics of a network node, according to the 1394 standard; and

[0040]FIG. 8 general contents of the register memory of a network node,according to the 1394 standard.

[0041]FIG. 1 shows the schematic representation of a network, which ismade up of six network nodes A through E. Forming the starting point ofthe network is network node A, which is designated as a root networknode and, as such, assumes the management of the network.

[0042] This network node A is assigned identity number phy_id=4. It hasthree network-node outputs, A, B, and C. An additional network node Bhaving identity number phy_id=1 is connected to network-node output A atport C, network node A being designated as a parent and subjacentnetwork node B being designated as a child.

[0043] Further network nodes C and D having identification numbersphy_id=0 und phy_id=2 are connected to network-node terminals A and B.These network nodes C and D form the end of the network and aretherefore designated as terminal nodes (leaf). They constitute, in turn,child nodes of network node B, which is a parent node in this respect.

[0044] An additional terminal node E having identification numberphy_id=3 is connected to network terminal B of root network node A.

[0045] The network topology is determined by the classification of thenetwork nodes as parent and child with respect to one another, as wellas by the physical characteristics of the network nodes and the devicesconnected to the network nodes. The network is particularly suitable fordigital audio and video applications, such as CD players, videorecorders, camcorders, monitors, etc. In the example shown, the rootnetwork node forms a transmission interface for a device according tothe Digital Audio Broadcast Standard DAB.

[0046]FIG. 2 shows an example of a change to the network from FIG. 1,network nodes D and E being interchanged. Identity number phy_id remainsa function of the position of the network node in the network, so thatnetwork node E obtains identification number phy_id=2 of network node D,which was previously at this position. The same applies to network nodeD, which obtains identification number phy_id=3.

[0047] The network, i.e. the individual network nodes are designed to beable to automatically detect the network topology. In this connection,the network topology is stored in a so-called topology map in the rootnode.

[0048] The determination of the network topology is outlined in FIG. 3.It can be seen that each network node has a register memory ROM, inwhich at least the network-node identity and the interconnectionconfiguration of the network-node outputs are stored. A uniquemanufacturing number, vendor-ID, and further information about thephysical characteristics of the network node are permanently writteninto each network node. The content will be discussed again later, withreference to FIGS. 5 through 8.

[0049] According to the IEEE-1394 standard, the current network topologyis automatically determined, as soon as a network node or device isremoved or added.

[0050] A reset is triggered after the removal or addition of the node.The assignments are made anew, i.e. a different node may become theroot. The transmission of the information proceeds in a partiallyindependent manner, without constant renewal of the demand by the rootnode.

[0051] Information from subordinate network nodes 0 through N-2 is thensupplied to the root network node, and the number of network nodes inthe network, identification numbers phy_id, information about thecommunication characteristics and physical characteristics of thenetwork nodes, etc. are stored in the so-called topology map. Thedetailed contents of the topology map are explained later on the basisof FIG. 5.

[0052] With the aid of the topology map, the communication in thenetwork is controlled by the root network nodes.

[0053] According to the present invention, a current comparison networktopology is now stored in the so-called ID-map memory, in that thecontents of the data are read out the topology map and out ofnetwork-node register memories ROM and stored in a specific manner inthe ID-map memory.

[0054] It can be seen from FIG. 4 that, when the network is initializedat the beginning, a reference network topology is stored on demand onthe basis of a current network topology that is intended to be used as areference network topology. To this end, the topology map and registermemory ROM of network nodes 0 to N−1 are read in, as is already sketchedin FIG. 3.

[0055] The network is automatically checked on demand or in response tothe network being reset, in that the current network topology iscompared to the reference network topology. According to the IEEE-1394standard, a reset is automatically carried out, for example, as soon asa network node or terminal equipment is added to or removed from thenetwork. A reset may also be triggered for other reasons, such as inresponse to the power mode being changed from standby-mode to on-mode.

[0056] The network is tested in such a manner, that the networkcomparison topology is determined by reading in the contents of the dataof the topology map and register memory ROM of the network nodes, andcompared to the permanently stored reference network topology(reference-ID map).

[0057] The changes to the network may be displayed on a monitor, e.g.printed out by a printer, but also corrected. The reference networktopology may be restored by automatically deactivating the improperlyadded network nodes or devices.

[0058] The contents of the data of the topology map according to theIEEE-1394 standard are shown in FIG. 5. The topology map is first madeup of basic information, such as the length, as well as basicinformation about the network, such as the node count and the number ofdata packets sent by the network nodes (self-ID count). In addition, thedata packets sent by the network nodes are sequentially stored.

[0059] The data packets sketched in FIG. 6 are sent by the network nodesto the root network node.

[0060] These data packets (self-ID packets) are essentially made up ofidentification number phy_id of the network node, the number of timeintervals (gap count), the speed (sp), the delay time (del), the voltageclass (pwr), and information regarding the network-node terminals P0,P1, and P2. The phy_id is automatically assigned by the reset processand is not a physical network-node characteristic stored in the memoryof the network node. Identification number phy_id is uniquely determinedby the order during the transmission of the self-ID packets inaccordance with the order child/parent with respect to each other.

[0061] The network topology may be uniquely determined on the basis ofthe data packets, using identification number phy_id, network-nodeterminals P0, P1, and P2, as well as the node count. The additionalinformation is not necessarily required for testing the network, but maybe helpful in detecting any manipulation at the network nodes orterminal equipment.

[0062] Accordingly, not the complete contents of the data but ratherjust the necessary data contents must be read out and compared to eachother during the reading-out of register memory ROM of the networknodes, as well as during the reading-out of the topology map forgenerating the network comparison topology or the reference networktopology.

[0063]FIG. 7 shows the minimum data content of the register memory of anetwork node, the minimum data content including header 01H and uniquemanufacturer identifier, vendor ID. Furthermore, the additionalinformation sketched in FIG. 8 may be stored in the register memory ofthe network nodes. The contents of these data are not of significance inthe following, so that reference is made to the IEEE-1394 standard.

[0064] For the network of the species, it is important for the networknodes to be designed to automatically generate the data packets (self-IDpackets) and to send them to the root network node, so that the physicalcharacteristics of the network nodes and the states of the correspondingnetwork-node terminals may be entered in the topology map.

[0065] The appropriate network-management procedures are usuallyimplemented in an appropriately specialized, integrated circuit (chip).Therefore, the testing of the network and the network management is notcarried out by a host computer, but rather by the appropriatelyspecialized, integrated circuits, or by software.

1. A method for testing a network made up of network nodes and devicesconnected to the network nodes, having the following steps: determiningthe network topology, using at least the number of network nodes, thenetwork-node identity, and the interconnection configuration of thenetwork-node inputs and outputs; comparing a current network topology toa stored, reference network topology for the network, in order to detecta change in the number and/or type of devices connected to the network,in the number and/or type of network topology, and/or in the numberand/or type of network nodes at which a change is present, restoring thereference network topology through automatic deactivation of networknodes, network-node outputs, and/or devices at the network nodes, whichare not provided in the reference network topology.
 2. The method asrecited in claim 1, a current network topology being stored as areference network topology by reading in the data for the currentnetwork topology from a central network-topology memory for the network,and from decentralized network-node memories; and storing the data readin in a reference network-topology memory.
 3. The method as recited inclaim 1, wherein the testing is carried out automatically in response tothe network being reinitialized.
 4. The method as recited in one ofclaims 1 through 3, characterized by reading in the data for the currentnetwork topology from a central network-topology memory for the network,and from decentralized network-node memories; storing the data read inin a network-topology comparison memory, comparing the current networktopology to the reference network topology by comparing the contents ofthe data stored in the network-topology comparison memory and in areference network-topology memory.
 5. The method as recited in one ofthe preceding claims, a network corresponding to the IEEE-1394 standardbeing tested.
 6. A network having network nodes interconnected in anetwork topology, and having devices at network nodes, each network nodehaving memory to store data for indicating at least the network-nodeidentity and the interconnection configuration of the network-nodeoutputs, and the network being designed to determine the current networktopology, using at least the number of network nodes, the network-nodeidentity, and the wiring of the network-node outputs, by reading out thememory of the network nodes; characterized by a memory for storing areference network topology for the network; a comparator for comparingthe current network topology to the stored, reference network topologyfor the network, in order to test the network and detect a change in thenumber and/or type of devices connected to the network, in the numberand/or type of network topology, and/or in the number and/or type ofnetwork nodes at which a change is present, and wherein the network isdesigned for restoring the reference network topology by automaticallydeactivating network nodes, network-node outputs, and/or devices at thenetwork-node outputs, which are not provided in the reference networktopology.
 7. The network as recited in claim 6, wherein the network isdesigned to automatically store, on demand, the detected, currentnetwork topology as a reference network topology in the memory for thereference network topology.
 8. The network as recited in claim 6 or 7,wherein the network is designed for automatic testing of the networkafter reinitialization or the addition or removal of a networkcomponent.
 9. The network as recited in one of claims 6 through 8,characterized by a network-topology comparison memory for storing thedetected, current network topology, the comparator being designed tocompare the contents of the data stored in the network-topologycomparison memory and in the reference network-topology memory.
 10. Thenetwork as recited in one of claims 6 through 9, wherein the networkcorresponds to the IEEE-1394 standard.